Monocarboxylate salts of imidazole reaction products, process for preparing the salts, and surface treatments, additives for resins, and resin compositions, containing the same

ABSTRACT

The present invention provides a novel imidazole/organic monocarboxylic acid salt derivative reaction product capable of improving the adhesion between a resin and a metal such as copper, steel or aluminum, or an inorganic material such as glass fiber, silica, aluminum oxide or aluminum hydroxide, a method for producing this imidazole/organic monocarboxylic acid salt derivative reaction product, and a surface treatment agent, resin additive and resin composition that use this imidazole/organic monocarboxylic acid salt derivative reaction product.  
     The above imidazole/organic monocarboxylic acid salt derivative reaction product is obtained by reacting an imidazole compound represented by undermentioned general formula (1) with a silane compound having a glycidoxy group represented by undermentioned general formula (2) at 80 to 200° C., and then reacting the product thus obtained with an organic monocarboxylic acid at 50 to 200° C.

TECHNICAL FIELD

[0001] The present invention relates to a novel imidazole/monocarboxylicacid derivative, and also to a surface treatment agent that has thisimidazole/monocarboxylic acid derivative as an active ingredient and isfor improving the adhesion between a metal such as copper, steel oraluminum or an inorganic material such as glass fiber, silica, aluminumoxide or aluminum hydroxide and a resin, a resin additive that has thisimidazole/monocarboxylic acid derivative as an active ingredient and isfor improving the adhesive strength and mechanical strength of a resinsuch as an epoxy resin, and a resin composition—in particular apolyimide resin composition —that contains this imidazole/monocarboxylicacid derivative.

BACKGROUND ART

[0002] A board of an electronic device is made by heating copper foiland a phenol-resin-impregnated paper substrate, anepoxy-resin-impregnated glass substrate or the like while pressurizingto produce a copper-clad laminate, and then forming an electric networkby etching, and mounting elements such as semiconductor devices on top.

[0003] During the manufacturing process, the copper foil is bonded tothe substrate, and they are heated, immersed in acidic or alkalinesolutions, applied a resist ink, soldered, and hence the copper foil andthe substrate are required to have various properties. To satisfy theserequirements, with regard to the copper foil, studies have been carriedout into subjecting the copper foil to brass layer formation treatment(Japanese Patent Publication Nos. 51-35711 and 54-6701), chromatetreatment, zinc-chromium mixture coating treatment in which the coatingincludes zinc or zinc oxide and chromium oxide (Japanese PatentPublication No. 58-7077), treatment with a silane coupling agent, andthe like. Moreover, with regard to the resin, the requirements aresatisfied by changing the type of resin and/or curing agent and/or themixing proportions thereof, by adding additives, and so on. Moreover, inthe case of glass fiber, surface treatments using a silane couplingagent or the like have been studied. However, in recent years, therehave been advances in miniaturization of printed circuits, and theproperties required of the boards used in electronic devices have becomeever more stringent.

[0004] To cope with the required improvement in etching precision thatgoes along with the above, the Matte side of the copper foil bonded tothe prepreg is required to have a lower surface roughness (i.e. a lowprofile). However, the surface roughness of the Matte side produces ananchoring effect so as to bond the prepreg tightly, and hence therequirement of a low profile goes against improving the adhesivestrength, meaning that the reduction in the anchor effect upon loweringthe profile must be compensated for by improving the adhesive strengthby another means.

[0005] Moreover, a composite material in which an inorganic materialsuch as silica or alumina is filled into an epoxy resin matrix is usedas an electrically insulating casting material used, for example, inhigh voltage/high capacity devices and in sealing semiconductors inpower plants. Various electrical and mechanical properties are requiredof such a material, and to satisfy these requirements it is necessary toimprove the adhesion between the inorganic material and the resin.Measures such as adding a silane coupling agent into the resin orsubjecting the inorganic material to surface treatment with a silanecoupling agent have been proposed, but yet further improvement of theresin/inorganic material interface is required.

DISCLOSURE OF THE INVENTION

[0006] An object of the present invention is to provide a novelimidazole/organic monocarboxylic acid salt derivative reaction productthat is capable of meeting these requirements, that is, that improvesthe adhesion between a metal such as copper, steel or aluminum or aninorganic material such as glass fiber, silica, aluminum oxide oraluminum hydroxide and a resin. Further, another object of the presentinvention is to provide a method for producing this imidazole/organicmonocarboxylic acid salt derivative reaction product, and a surfacetreatment agent, resin additive and resin composition that use thisimidazole/organic monocarboxylic acid salt derivative reaction product.

[0007] The inventors of the present invention carried out assiduousstudies, and as a result discovered: if a metal or an inorganic materialis subjected to surface treatment with an imidazole/organicmonocarboxylic acid salt derivative reaction product obtained byreacting a specific imidazole compound with a silane compound having aglycidoxy group and then reacting with an organic monocarboxylic acid,then the adhesion of the metal or the inorganic material to a resin isimproved; and furthermore, if such an imidazole/organic monocarboxylicacid salt derivative reaction product is added to a resin such as anepoxy resin, then the curing reaction of the resin is promoted andmoreover the adhesive strength and the mechanical strength of the resinare improved.

[0008] The present invention was achieved based on the above findings,and is summarized as follows:

[0009] (1) An imidazole/organic monocarboxylic acid salt derivativereaction product obtained by reacting an imidazole compound representedby undermentioned general formula (1) with a silane compound having aglycidoxy group represented by undermentioned general formula (2) at 80to 200° C., and then reacting with an organic monocarboxylic acid at 50to 200° C.;

[0010] where, in general formulae (1) and (2), R¹, R² and R³ are eachindependently a hydrogen atom, a vinyl group, or an alkyl group having 1to 20 carbon atoms, while R² and R³ may together form an aromatic ring;R⁴ and R⁵ are each independently an alkyl group having 1 to 5 carbonatoms; m is an integer between 1 and 10; and n is an integer between 1and 3.

[0011] (2) A method for producing the imidazole/organic monocarboxylicacid salt derivative reaction product as described in (1) above,comprising: reacting an imidazole compound represented by undermentionedgeneral formula (1) with a silane compound having a glycidoxy grouprepresented by undermentioned general formula (2) at 80 to 200° C.; andsubsequently reacting with an organic monocarboxylic acid at 50 to 200°C.;

[0012] where, in general formulae (1) and (2), R¹, R², R³, R⁴, R⁵, m andn are as defined in (1) above.

[0013] (3) A surface treatment agent having the imidazole/organicmonocarboxylic acid salt derivative reaction product as described in (1)above as an active ingredient.

[0014] (4) A resin additive having the imidazole/organic monocarboxylicacid salt derivative reaction product as described in (1) above as anactive ingredient.

[0015] (5) A resin composition containing the imidazole/organicmonocarboxylic acid salt derivative reaction product as described in (1)above.

[0016] (6) A polyimide resin composition containing theimidazole/organic monocarboxylic acid salt derivative reaction productas described in (1) above.

[0017] Following is a more detailed description of the presentinvention.

[0018] In above-mentioned general formulae (1) and (2), if any of R¹, R²or R³ is an alkyl group, then this alkyl group has 1 to 20 carbon atoms,preferably 1 to 12 carbon atoms. Moreover, if R² and R³ together form anaromatic ring, then this aromatic ring is preferably a benzene ring.

[0019] The imidazole/organic monocarboxylic acid salt derivativereaction product of the present invention can be manufactured byreacting an imidazole compound represented by undermentioned generalformula (1) with a silane compound having a glycidoxy group representedby undermentioned general formula (2) at 80 to 200° C., and thenreacting with an organic monocarboxylic acid at 50 to 200° C. Thereaction mechanism is complicated, with networking through siloxanebonds occurring in part, but the main reactions can be represented bythe following formulae.

[0020] In the above general formula, A indicates the organicmonocarboxylic acid.

[0021] Preferable examples of the imidazole compound represented byabove-mentioned general formula (1) include imidazole,2-alkylimidazoles, 2,4-dialkylimidazoles and 4-vinylimidazole. Of these,particularly preferable ones include imidazole; as 2-alkylimidazoles,2-methylimidazole, 2-ethylimidazole and 2-undecylimidazole; and as a2,4-dialkylimidazole, 2-ethyl-4-methylimidazole. Moreover, examples ofthe silane compound having a glycidoxy group represented byabove-mentioned general formula (2) are3-glycidoxypropyltrialkoxysilanes, 3-glycidoxypropyldialkoxyalkylsilanesand 3-glycidoxypropylalkoxydialkylsilanes. Of these, particularlypreferable ones include, as 3-glycidoxypropyltrialkoxysilanes,3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane;as a 3-glycidoxypropyldialkoxyalkylsilane,3-glycidoxypropyldimethoxymethylsilane; and as a3-glycidoxypropylalkoxydialkylsilane,3-glycidoxypropylethoxydimethylsilane. Moreover, as the organicmonocarboxylic acid, a saturated aliphatic monocarboxylic acid, anunsaturated aliphatic monocarboxylic acid, an aromatic monocarboxylicacid or the like can be used. Of these, particularly preferable onesinclude acrylic acid, methacrylic acid, isobutyric acid, octylic acid,formic acid, glyoxylic acid, crotonic acid, acetic acid, propionic acid,benzoic acid, salicylic acid, cyclohexanecarboxylic acid, toluic acid,phenylacetic acid and p-t-butylbenzoic acid.

[0022] The reaction of the imidazole compound and the silane compoundhaving a glycidoxy group is carried out using the synthesis methoddisclosed in Japanese Patent Application Laid-open No. H5-186479.Specifically, the imidazole compound and the silane compound having aglycidoxy group can be reacted by heating the imidazole compound to atemperature of 80 to 200° C. and then instilling the silane compoundhaving a glycidoxy group into the imidazole compound in a ratio of 0.1to 10 mol of the silane compound per 1 mol of the imidazole compound,and in this case the reaction time is adequate at about 5 minutes to 2hours. There is no particular need for a solvent, but an organic solventsuch as chloroform, dioxane, methanol or ethanol may be used as areaction solvent. Note that the reaction is damaged by water, and isthus preferably proceeded under an atmosphere of a gas containing nomoisture such as dried nitrogen or argon so that no moisture gets intothe system. The desired imidazole-silane compound represented as theabove general formula is obtained as a mixture with other compoundshaving siloxane bonds, but the desired compound can be isolated andpurified by a known method that utilizes the difference in solubilitybetween the compounds or column chromatography. Note, however, that inthe case of use as a surface treatment agent or a resin additive, thereis no real need to isolate the imidazole-silane compounds from oneanother, and the reaction mixture containing complex compounds partiallynetworked through Si—O bonds can be used as it is in the next reactionstep, namely the reaction with the organic monocarboxylic acid. Theimidazole-silane compounds so obtained reacts with the organicmonocarboxylic acid by heating the imidazole-silane compounds to atemperature of 50 to 200° C., and then adding, for example, anequivalent molar amount of the organic monocarboxylic acid; the reactiontime is again adequate at about 5 minutes to 2 hours. Again, there is noparticular need for a solvent, but an organic solvent such aschloroform, dioxane, methanol and ethanol may be used as a reactionsolvent. Moreover, again the reaction is damaged by water, and is thuspreferably advanced under an atmosphere of a gas containing no moisturesuch as dried nitrogen or argon so that no moisture gets into thesystem.

[0023] The imidazole/organic monocarboxylic acid salt derivativereaction product of the present invention usefully serves as a surfacetreatment agent or a resin additive for improving adhesion. When used asa surface treatment agent, the imidazole/organic monocarboxylic acidsalt derivative reaction product of the present invention is preferablyused as a solution with a suitable solvent. Moreover, when used as aresin additive, the reaction product may either be used as is or as asolution in a suitable solvent, with the amount added being 0.01 to 50parts per weight, preferably 0.1 to 20 parts per weight, per 100 partsper weight of the resin. Moreover, substrates to which the surfacetreatment agent of the present invention can be applied includesubstrates made of a metallic material such as copper, iron or aluminumor an inorganic material such as glass fiber, silica, aluminum oxide oraluminum hydroxide. Moreover, when adding the imidazole/organicmonocarboxylic acid salt derivative reaction product of the presentinvention to a resin to improve the adhesion and strength of the resin,resins that can be used include polyimide resins, phenol resins, urearesins, melamine resins, unsaturated polyester resins, diallyphthalateresins, polyurethane resins, silicon resins, vinyl chloride resins,vinylidene chloride resins, vinyl acetate resins, polyvinyl alcoholresins, polyvinyl acetal resins, polystyrene resins, AS resins, ABSresins, AXS resins, methacrylate resins, polyethylene resins, EVAresins, EVOH resins, polypropylene resins, fluororesins, polyamideresins, polyacetal resins, polycarbonate resins, saturated polyesterresins, polyphenylene ether resins, polyphenylene sulfide resins,polyarylate resins, polysulfone resins, polyethersulfone resins,polyetheretherketone resins, liquid crystal plastic resins, celluloseplastic resins, thermoplastic elastomer resins, alkyd resins, furanresins, acrylic acid ester resins, petroleum resins, dicyclopentadieneresins, diethylene glycol bis(allyl carbonate) resins, and polyparabanicacid resins.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 is a ¹H-NMR spectrum of the imidazole/methacrylic acid saltderivative synthesized in Example 1;

[0025]FIG. 2 is a ¹³C-NMR spectrum of the imidazole/methacrylic acidsalt derivative synthesized in Example 1 ;

[0026]FIG. 3 is a ²⁹Si-NMR spectrum of the imidazole/methacrylic acidsalt derivative synthesized in Example 1; and

[0027]FIG. 4 is an FT-IR spectrum of the imidazole/methacrylic acid saltderivative synthesized in Example 1.

BEST MODE FOR CARRYING OUT THE INVENTION

[0028] Following is a more detailed description of the present inventionwith examples.

[0029] Synthesis of the imidazole/organic carboxylic acid saltderivative

EXAMPLE 1

[0030] Imidazole 13.62 g (0.2 mol) was melted at 95° C., and 47.27 g(0.2 mol) of 3-glycidoxypropyltrimethoxysilane was instilled thereinover 30 minutes while stirring under an argon atmosphere. After theinstillation had been completed, the reaction was continued for afurther 1 hour at a temperature of 95° C., thus obtainingimidazole-silane compounds. The reaction solution was then kept at atemperature of 80° C. while instilling therein 17.2 g (0. 2 mol) ofmethacrylic acid over 30 minutes. After the instillation had beencompleted, the reaction was proceeded for a further 30 minutes at atemperature of 80° C., thus obtaining a reaction product containing thecompound represented by undermentioned formula (1-1) along with othercomplex compounds having siloxane bonds. The reaction product wasobtained as a viscous transparent orange liquid. The ¹H-NMR spectrum,¹³C-NMR spectrum, ²⁹Si-NMR spectrum and FT-IR spectrum of the obtainedimidazole/methacrylic acid salt derivative are shown in FIGS. 1, 2, 3and 4, respectively.

[0031] Imidazole 13.62 g (0.2 mol) was heated to 95° C., and 47.27 g(0.2 mol) of 3-glycidoxypropyltrimethoxysilane was instilled thereinover 30 minutes while stirring under an argon atmosphere. After theinstillation had been completed, the reaction was advanced for a further1 hour at a temperature of 95° C., thus obtaining imidazole-silanecompounds. The reaction solution was then kept at a temperature of 80°C. while adding therein 51.28 g (0.2 mol) of palmitic acid over 30minutes. After the addition had been completed, the reaction wascontinued for a further 30 minutes at a temperature of 80° C., thusobtaining a reaction product containing the compound obtained in Example1 but with palmitic acid substituted for methacrylic acid. The reactionproduct was obtained as a viscous transparent orange liquid.

EXAMPLE 3

[0032] Application as a Surface Treatment Agent (1)

[0033] Surfaces of aluminum alloy plates (A2024P made by Nihon TestPanels conforming to JIS H4000; size 25×100 mm, thickness 1.6 mm) weretreated by immersing the plates in a 0.4% methanol solution of theimidazole/methacrylic acid salt derivative synthesized inabove-mentioned Example 1 and then drying with a blow of hot air. Twosuch surface-treated aluminum alloy plates were bonded together using aresin composition (Epicote 828 (an epoxy resin made by Yuka Shell Epoxy)100 parts; dicyandiamide (made by Kanto Kagaku) 5 parts;2-ethyl-4-methylimidazole (made by Shikoku Kasei) 1 part) with curingconditions of 1 hour at 100° C. plus 1 hour at 150° C., and then a testfor adhesive strength of the adhered samples against tensile shear wascarried out in accordance with JIS K6850. Moreover, for comparison,untreated aluminum alloy plates and aluminum alloy plates treated with a0.4% solution of 3-glycidoxypropyltrimethoxysilane in methanol wereevaluated in the same way. The results are shown in Table 1. TABLE 1Test results of adhesive strength against tensile shear Adhesivestrength Treatment agent (KN/cm²) Imidazole/methacrylic 1.25 acid saltderivative 3-glycidoxypropyl- 0.79 trimethoxysilane Untreated 0.75

[0034] Application as a Surface Treatment Agent (2) (Evaluation ofSolubility)

[0035] The solubilities of the imidazole/organic monocarboxylic acidsalt derivatives in various solvents were evaluated. The evaluationmethod was to bring the imidazole/organic monocarboxylic acid saltderivative into a solvent so as to be 1 wt %, and stir, and thenvisually observe whether or not the imidazole/organic monocarboxylicacid salt derivative dissolves. The results are shown in Table 2. TABLE2 Evaluation of solubility Ethyl Water Methanol Acetone acetate TolueneHexane Imidazole/ ◯ ◯ X X ◯ Δ methacrylic acid salt derivative 1)Imidazole/ X ◯ ◯ ◯ ◯ ◯ palmitic acid salt derivative 2) Δ4) ◯ X X X XImidazole- silane 3)

[0036] It is obvious from Table 2 that the imidazole/organic Example 1and 2 exhibit superior solubility in various solvents compared with animidazole-silane not modified with an organic monocarboxylic acid.

Example 4

[0037] Application as a Resin Additive (1) (Improvement in Adhesion)

[0038] Two untreated aluminum alloy plates were bonded together using anepoxy resin composition (Epicote 828 100 parts; dicyandiamide (made byKanto Kagaku) 5 parts; the imidazole/methacrylic acid salt derivativeobtained in Example 1, 1 part) with curing conditions of 1 hour at 100°C. plus 1 hour at 150° C., and then an adhesive strength of the adheredplates against tensile shear was tested in accordance with JIS K6850.The results are shown in Table 3. Moreover, for comparison, anothersample adhered using 1 part of 2-ethyl-4-methylimidazole in place of theimidazole/carboxylic acid salt derivative was evaluated in the same way.The results are shown in Table 3. TABLE 3 Test results of adhesivestrength against tensile shear Adhesive strength Additive (KN/cm²)Imidazole/methacrylic 1.18 acid salt derivative 2-ethyl-4-methyl- 0.75imidazole

[0039] Application as a Resin Additive (2) (Improvement in MechanicalStrength)

[0040] Epicote 828 (a bisphenol A type epoxy resin) made by Yuka ShellEpoxy was used as a resin, 11.28 g (2.89×10⁻² mol) of theimidazole/methacrylic acid salt derivative obtained in Example 1 wasmixed in as a curing agent per 100 g of the epoxy resin, the mixture wascured with conditions of 1 hour at 100° C. plus 1 hour at 150° C. toproduce a cured epoxy resin, and then the flexural strength wasmeasured. The results are shown in Table 4. Moreover, for comparison,the same evaluation was carried out using an epoxy resin cured with2-ethyl-4-methylimidazole, which is a commonly used imidazole curingagent. TABLE 4 Improvement in mechanical strength Flexural strengthCuring agent (N/mm²) Imidazole/methacrylic 105.2 acid salt derivative2-ethyl-4-methyl- 99.9 imidazole

[0041] Application as a Resin Additive (3) (Improvement in AdhesiveStrength)

[0042] The imidazole/methacrylic acid salt derivative obtained inExample 1 was added to a 20 wt % solution of a polyimide precursorhaving a polyamidic acid (a polymer obtained by reacting diaminodiphenyl ether with pyromellitic acid anhydride) as the main constituentthereof in N-methylpyrrolidone such that the amount of theimidazole/methacrylic acid salt derivative relative to the resin was 1wt %, and the resulting mixture was cast onto the lustrous surface of apiece of loz copper foil. The cast film was cured under heatingconditions of 30 minutes at 120° C., followed by 10 minutes at 150° C.,followed by 10 minutes at 200° C., followed by 10 minutes at 250° C.,followed by 10 minutes at 350° C., thus forming a 25-micron polyimidecoating film on the copper foil. The adhesive strength of the laminateso obtained was then evaluated as the peel strength. The results were asfollows. Peel strength (kg/cm) Imidazole/methacrylic acid 1.2 saltderivative added Imidazole/methacrylic acid 0.5 salt derivative notadded

INDUSTRIAL APPLICABILITY

[0043] By using the imidazole/organic monocarboxylic acid saltderivative of the present invention as a surface treatment agent or aresin additive, the adhesion between a metal and a resin is improved.The imidazole/organic monocarboxylic acid salt derivative of the presentinvention is thus ideal for use in adhesives, encapsulants, coatingmaterials, laminate materials, molding materials, printed circuitboards, semiconductor chip coating materials, semiconductor chipmounting materials, photosensitive materials such as photoresists, andthe like when adhesiveness is important. Moreover, the imidazole/organicmonocarboxylic acid salt derivative of the present invention can be usedas a curing agent for a resin, improving the adhesive strength and themechanical strength of the resin.

1. An imidazole/organic monocarboxylic acid salt derivative reactionproduct obtained by reacting an imidazole compound represented byundermentioned general formula (1) with a silane compound having aglycidoxy group represented by undermentioned general formula (2) at 80to 200° C., and then reacting with an organic monocarboxylic acid at 50to 200° C.;

where, in general formulae (1) and (2), R¹, R² and R³ are eachindependently a hydrogen atom, a vinyl group, or an alkyl group having 1to 20 carbon atoms, while R² and R³ may together form an aromatic ring;R⁴ and R⁵ are each independently an alkyl group having 1 to 5 carbonatoms; m is an integer between 1 and 10; and n is an integer between 1and
 3. 2. A method for producing the imidazole/organic monocarboxylicacid salt derivative reaction product according to claim 1, comprising:reacting an imidazole compound represented by undermentioned generalformula (1) with a silane compound having a glycidoxy group representedby undermentioned general formula (2) at 80 to 200° C.; and subsequentlyreacting with an organic monocarboxylic acid at 50 to 200° C.;

where, in general formulae (1) and (2), R¹, R², R³, R⁴, R⁵, m and n areas defined in claim
 1. 3. A surface treatment agent having theimidazole/organic monocarboxylic acid salt derivative reaction productaccording to claim 1 as an active ingredient.
 4. A resin additive havingthe imidazole/organic monocarboxylic acid salt derivative reactionproduct according to claim 1 as an active ingredient.
 5. A resincomposition containing the imidazole/organic monocarboxylic acid saltderivative reaction product according to claim
 1. 6. A polyimide resincomposition containing the imidazole/organic monocarboxylic acid saltderivative reaction product according to claim 1.